1. Field of the Invention
The present invention relates to a cathode-ray tube, having an antistatic film on the outer surface of a front panel, and a method for manufacturing the same.
2. Description of the Prior Art
An electrostatic charge is accumulated on the outer surface of the front panel of a cathode-ray tube during or after the operation of the tube. Thus, dust is attracted to the outer surface of the cathode-ray tube, and an operator may suffer from an electric shock, if he or she touches the outer surface of the cathode-ray tube.
Japanese Patent Disclosures (Kokai) No. 61-118932 and (Kokai) No. 61-118946 disclose a cathode-ray tube having an uneven surface made of SiO.sub.2 having a silanol group and formed on the outer surface of the front panel, Japanese Patent Disclosure (Kokai) No. 61-16452 discloses a cathode-ray tube having a film mainly composed of silicate material and an inorganic metallic compound and formed on the outer surface of the front panel.
The silanol group method for preventing charging utilizes the phenomenon that the silanol group adsorbs moisture in the air, thereby reducing the outer surface resistance with the moisture. Since this method utilizes the moisture in the air, the degree of effectiveness in preventing the charge depends upon the amount of moisture in the air. Thus, in a dry season or a district of low humidity, this method will not work effectively.
The method for preventing charging, wherein the film made of the silicate material and the inorganic metallic compound is used, cannot reduce the electric resistance of the film when an inorganic metallic compound such as SiO.sub.2 having a certain degree conductivity, does not exist in the film. If the compound having conductivity, such as SiO.sub.2, exists in a sufficient amount for reducing the electric resistance of the film, the strength of the antistatic film decreases, and the film cannot be used in practice.
Such a conventional cathode-ray tube involves a large deviation in the electric resistance value, or insufficiency in the strength of the antistatic film.